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I have a duplex with a flat roof. In the past tar and felt were applied and that never lasted very long. Insurance is paying for a new roof. What type of roofing will be the best thing long term. Just don't want to get calls everytime it rains.

You don't have many options for a flat roof, edpm rubber, or torch down modified are the only things I have seen that will hold up for many years, and probably your ony choices,if they do the torch dowm make sure they do all 3 stepas, backer fireproof membrane, then 1 layer torch down, then finish layer with texture coatings, stone, etc. This is all I have seen lately. Tar and stone is mostly gone now, as it is very costly and dangerous.Maybee a few local roofers or board members can give more imput! Good Luck

Am waiting on one local roofer to get back with me. (He hasn't been out there yet) but suggested some sort of TPO material might work. Another roofer suggested Modified Roll Roof but I've not heard anything good about that product.

TPO is becoming popular because it is a white membrane and reflects the sun.
Modified bitumen is similar to the old built up roof, but is generally a better product. It too can have a white surface. I know of a county in MD that will use nothing else on flat roofs.
EPDM membrane has been around for a while and performs well, but has a limited lifespan due to UV degradation.
In general all these systems will work well if they are properly detailed & applied. The proper roof pitch is required, usually at least 1/4"/ft is recommended. Nothing lasts forever and annual inspection & maintenance will help.

I'm with ed21 on this one- especially when he speaks about install quality. You need the best, most experienced roofer you can find for a flat roof system. Yeah, they will cost more initially but the payoff is problem-free endurance. Of all the flat-roof problems I've seen, about half were poorly done installs and the other half were structure-related. Go at this as if you want the best possible results no matter the cost and you'll be happy. Try to cut corners and you'll be back here soon seeking repair advice.

I would also recommened you rubber roofing. It has many advantages over other roofing materials like it is durable, energy efficient, light in weight etc. It is also wheather proof and require low maintainance.

I am not familiar with all the flat roof options, but I'd suggest that you talk with a roofer that does commercial buildings instead of a residential roofer. Flat roofs are common in commercial buildings.